Control system



Nov. 25, 1930. R. Y. McCULLOUGH 1,783,048

CONTROL SYSTEM Filed Jan. 22. 1929 Inventor- RobehtYMoCuHou gh WW Hts Attorney.

Patented Nov. 25, 1930 UNETED STATES PATENT orrica ROBERT Y. MCOULLOUGH, F SCHENECTADY, NEW YORK, ASSIGNOR 'IO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NE'W YORK CONTROL SYSTEM Application filed January 22, 1929.

My invention relates to control systems and particularly to a system for automatically controlling the connections between a plurality of normally independently energized circuits and an auxiliary source of current therefor.

One object of my invention is to provide an arrangement for automatically connect ing two normally independently energized 1o circuits together when either of the circuits becomes deenergized while the other is energized, and for automatically connecting both of the circuits to an auxiliary source of current when both of the circuits are simultaneously deenergized.

Another object of my invention is to provide an arrangement whereby an overload on either of two circuits when they are connected together and to an auxiliary source efi'ects the disconnection of the overloaded circuit from the auxiliary source and prevents'the reconnection of the disconnected circuit thereto whereas an overload on either of the two circuits when they are connected together but are not connected to the auxiliary source merely efiects the disconnection of said circuits from each other without preventing the automatic reconnection thereof to the auxiliary source.

My invention will be better understood from the following description when taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the accompanying drawing, which diagrammatically shows an arrangement embodying my invention for controlling the connections between two normally disconnected circuits and an auxiliary source of current,

1 and 2 represent two electric circuits, which for example, may be separate sections of a railway signalling system. The circuits 1 and 2 are normally disconnected from each other and are normally energized, independently of each other, from the same or difi'erent source of current. As shown in the drawing, the circuit 1 is arranged to be connected to a suitable source of current 3 by means of an overload circuit breaker 4 and the circuit 2 is arranged to be connected to a suit.-

Serial No. 334,314.

able source of current 5 by means of an overload circuit breaker 6. The circuit breakers l and 6 may be of any suitable type examples of which are wel known in the art.

The circuits 1 and 2 are arranged to be connected together by means of a connecting bus 7 which is arranged to be connected to the circuits 1 and 2 by means of suitable switches 8 and 9 respectively. 10 represents an auxiliary source of current which is aran ranged to be connected to the connecting bus- 7 by means of a suitable switch 11 so that it supplies current to both of the circuits 1 and 2 when the switches 8, 9 and 11 are closed. as

in certain systems of electric distribution such as railway signalling systems, it is very essential that the various sections of the system should be energized at all times. There fore, it is necessary to provide an arrangement for reenergizing a deenergized section from some other source as soon as possible after the normal source supplying current thereto fails. In accordance with my invention I provide an arrangement whereby a 5 predetermined decrease in the voltage across either the circuit 1 or 2 while the other is normally energized eiiects the closing of the switches 8 and 9 so that the circuits are connccted together and the deenergized circuit is supplied from the normal circuitand whereby the auxiliary source 10 is connected to both of the circuits to supply current thereto when the voltages across both of the circuits 1 and 2 simultaneously remain below predetermined values for a predetermined time.

For accomplishing these results, I provide two time relays 14 and 15 which are respectively connected so that they are energized so in response to the voltages across the circuits 1 and 2. The relay 1 1 is arranged to efiect the energization of a control relay 16 when the voltage across the circuit 1 remains above a predetermined value for a predetermined time and to eflect the deenergization of the control relay 16 when the voltage across the circuit 1 remains below a predetermined value for a predetermined time. lVhen the control relay 16 is energized and the auxiliary P source 10 is disconnected from the bus 7, the control relay 16 is arranged to complete an energizing circuit for a control relay 17.

The time relay15 is connected so that it is energized in accordance with the voltage across the circuit 2 and is arranged to effect the energization of the control relay 18 when the voltage across the circuit 2 remains above a predetermined value for a predetermined time and to efl ect the deenergization of the control relay 18 when the voltage across the circuit 2 remains below a predetermined value for a predetermined time. .Vhen'the control relay 18 is energized and the auxiliary source 10 is disconnected from the bus 7 the control :relayl8 is arranged to'completean energizing circuit for a control relay 19. l/Vhen the voltage across the circuit 1 is normal so that control relay 17' is energized and the voltage, across the other circuit 2 is :below a predetermined value so'that the contacts 20 otthetimerelaylli are closed, an energizing circuit'is completed fora control relay 22 which when energized completes'an energizingcircuit for the'closing coil 23 of the switch 8. The switch 8 when closed connects thecircuit 1' to the connecting bus 7 and also completes an energizing circuit for the. control. relay 24; which, in turn, completes an energizing circuit for the closing coil 25 of the switch 9 so that circuit 2 is also connected to the bus 7 1 1 I W hen the voltage across the circuit 2 is normal so thatcontrol relay 19 is energized and the voltage across the circuit 1 is belowa. predetermined valueso that the contacts 28 of the time relay 14 are closed, an energizing circuit is completed for the control. relay 2 1 which, in turn, completes an energizing circuit for the closing coil 25 of the switch 9 to connect the circuit 2 to the connecting bus 7. The closing of the switch 9 alsocompletes an energizing circuit for the control relay 22 which, in turn, completes an energizing circuit for the closing coil 23 0t theswitch 8 so that the circuit 1 is also connected to the connecting bus 7. 1

In order to: effect the connection of the auxiliary source 10 to the'bus 7 and to both of the circuits 1 and 2 when they are simultane ously deener'gizechl provide a voltage relay 30 which is connected so as to be responsive to the voltage of the auxiliary source 10. VJhen th'eauxiliary source voltage is above a predetermined value, the voltage relay main tains its contacts 31 closed and when the auX- iliary source voltage is below a predetermined value the relay 3O maintains its contact 31 opened. I also provide a control relay 32 which is controlled by the relays 16 and 18 so that it is energized when the voltage of both of the circuits 1 and 2 are-below predetermined values. WV hen the relays 30 and 32 are simultaneously energized, a circuit is completed for a control relay 33 which l0 which isconnected in any suitable manner so that it is energized in accordance with the current through the switch 8. As shown in the drawing, the lockout relay 40 is connected to'the secondary of a current transformer 41, the primary of which is connected in series with the circuit 1 when the switch 8 is closed.- The lockout relaylO. is arranged to open contacts in the circuit 'ofthe control relay 22' and thereby effect the opening, of switch 8 whenthe current throughthe switcl 8 exceeds a predetermined value. 5 1

The opening of the switch 9 is effected in a similarmanner by means ofa lockout relay l2 which is connected to the secondary ot a current transformer 43, the primary. of which is connected in serieswiththe circuit 2 when the switch 9 is closed. The lockout relay 42 is arranged to open contacts in the circuit of the control relay 24' when the current through the switch 9gexceeds a predetermined Value. a

The lockout relays lOand 42 are preterably arranged in'any suitablemannerlexamples of which ar-e well knowninthe art, so thatthe resettingot their respective con-. tacts is manually controlled so that a sub-, sequent automatic reclosingof theassociated switch cannot be effected until an operator hashad an opportunity to investigate and determine whether or: not the conditions war rant the reclosing otthe locked out switch.

In accordance withmy invention. I provide an arrangement whereby the lookout relays 40 and 42 operate'to effect the locking out of their associated switches only when the: auxiliary source 10 is supplyingfcurrent to the connecting bus 7. This result is ac complished in the particular 7 arrangement shown in the drawing by providing the switch 11 with auxiliary contactswliich shunt the operating'coils of the lockout relays l0 and 42 when the switch 11 is open. Such an arrangement is desirable in order to prevent both of the switches. 8 and- 9 from being locked out when'a fault occurs'on one; of the circuits when it is being supplied with current from the other circuit. W hen a fault occurs under such conditions it is desirable to have the normalcircuit disconnected trom'its source of current by means of its associated overload circuit breaker so that both of the circuits 1 and 2,become simultaneouslydeenergized and effect the connection of the auxiliary source 10- thereto. It the faultis still connected to one of the circuits When arsenic 3 the auxiliary source is connected to both of the circuits it is then desirable to have the lockout relay associated with the switch in the faulty circuit operate to efiect the locking out of the switch in the faulty circuit without elfectingthe opening of the switch between the auxiliary source and the normal circuit. I r I In order to supply current from the circuits 1 and 2 and the auxiliary source lOto operate the various control devices. I provide the potential transformers 44, 45' and 46 the primary windings of which are respectively connected across the circuits 1 and 2 and the source and the secondary windings of which are respectively connected by control switches 47, 48 and 49 to the control devices which are arranged to be energized therefrom.

The operation of the arrangement shown in the drawing is as follows. Under normal conditions the circuit breakers 4 and 6 are closed and the switches 8, 9 and 11 are open so that the circuits 1 and 2 are disconnected from each other and are respectively enerthe control relay 16 is also connected across the secondary of the transformer 44. When the relay 16 is energized and the switch 11 is open an energizing circuit is completed for the control relay 17 from one secondary terminal of the transformer 44 through switch 47, contacts 51 of the relay 16, conductor 52,- auxiliary contacts 58 on the switch 11, conductor54, coil of relay 17, conductor 55, control switch 47 to the other, secondary terminal of the transformer 44. Therefore, under nor mal operating conditions the relays 14,16 and 17 are energized.

After the control switch 48 is closed and the voltage across the circuit 2' has remained 5 above a predetermined value for a predetermined time, the relay which is connected directly across the secondary winding of the transformer by the control switch 48, closes its contacts 56 and connects the ind ing of the control relay 18 across the-secondary winding of the transformer 45. hen the control relay 18 is energized and the switch 11 is open, an energizing circuit is completed for the control relay 19 from one secondary terminal of the transformer 45 through control switch 48, conductor 58, contacts 59 of relay 18, concluctor60, auxiliary contacts 61 on switch 11, conductor 62,

Y coil of relay 19;onducto'r 55, control switch to the other secondary terminal of the transformer 45. Therefore, under normal operating conditions the control relays 15,18 and 19 are also energized.

I If the auxiliary source 10 is also energized,

ing of the contacts 50 effects the Ideenergization of the control relay 16 which, in turn, opens at its contacts 51 the above-traced circuit for the control relay 17. The closing of the contacts 28 of the relay 14 completes an energizing circuit for the control relay 24. This circuit is from one secondary terminal of the transformer 45 through the switch, 48, conductor 58, contacts 59 of relay 18, conductor 60, auxiliary contact 61 on switch 11, conductor 62, contacts 64 of relay 19, conductor 65, contacts 28 of relay 14, conductor 66, coil of relay 24, conductor 67, contact 68 of lockout relay 42, conductor 55, control switch 48 to the other secondary terminal of the transformer 45. Control relay 24 by closing its contacts 69 connects conductor 62- to conductor 66 and thereby completes a locking circuit for itself which is independent of the contacts 28 of the voltage relay 14 so that the control relay 24 is not deenergized by the subsequent energization of the circuit 1. Relay 24 by closing'its' contacts 70 completes an energizing circuit for the closing coil 25 of the switch 9 so as to effect the connection of the circuit 2 to the connecting bus 7. This energizing circuit of the closing coil 25Vis from one secondary terminal of the transformer 45 through the switch 48, conductor 58, contacts 59 of the relay 18, conductor 60, auxiliary contacts 61 on switch 11, conductor 62, contacts 70 of relay 24, conductor 71, closing coil 25 of switch 9, conductor 55, control switch 48 to the other secondary terminal of the transformer 45. The switch 9by closing its auxiliary contacts 72 completes an energiz ing circuit for the control relay 22. This energizing circuit is from one secondary terminal of the transformer 45 through the control switch 48, conductor 58, contacts 59 of relay 18, conductor 60, auxiliary contacts 61 on switch 11, conductor 62, auxiliary contact 72 on switch 9, conductor 73, contacts 74 of relay 33, conductor 75, coil of relay 22, conductor 76, contact 7 7 of lockout relay 40, conductor 55, control switch 48 to the other secondary terminal of the transformer 45. Relay 22 by closing its contacts 78 and 79 completes an energizing circuit for the closing coil 23 of the switch 8 so as to connect the circuit 1 to the connecting bus? which is al.-

ready connected to the energized circuit 2 by means of the switch 9." This energizing circuit for the closlng COll 23 is from one secondary terminalof the transformer 45 through the .control' switch 48, conductor 58, contacts 59 of relay 18, condu'ctor60, auxiliarycontacts 61 on switch 11, conductor62, auxiliary contacts on switch 9,:conductor-7 3, contact 74 of relay 33, conductor 75,contact 7 8 ,of relay 22, conductor;54, contact 79 of relay 22,, con ductor 8l,closing coil 23 of switch 8, conductor 55, control switch 48130 the other secondary terminal of the transformer 45; 7 As soon as the switch 8 closes and normal voltage is restored across the circuit, 1 the voltage relay 14 is energized. ,If the fault the voltage across the circuit-1 fails while the circuit 2 is energized the switches 8 and 9 are closed to'connectthe denergized circuit 1 to theenergized circuit 2. 1

If the fault is still'connectedto the circuit i whenthe switch 8 is closed,-,the fault causes the overload circuit breaker6 to disconnect the source 5 from the circuit -2sothat both.

ofthecircuitsil and 2 are deenergized. ;Consequently, all of the control devices except the relay 30 which is c'onnectedacross the sec-, ondary windingof the transformer :46, are also de'energized. I a j r r 1 Since the switch 11 is open, the fault on the circuit 1 does not effect the operation of the lookout relays 40 and 42 at this time because the operating coil ofcthe lockout relay 40 isfshortcircuited bythecontactsj ,94 of the relayi22,and.the auxiliary contacts 95 on switch 11 andthe operating coil ofthe lock out relay 42 is short-circuited by the contacts 96 of relay. 24"and "auxiliary. contacts 97 on the switch 11, l I" 1'. v v 1 1 When both'of thecontrol relays 16 and 18 are deenergized and therelay 30 is energized; an energizing circuit is completed for the controlrelayf 32..3This energizing cir- F cuit isfromon'e secondary terminal of the transformer 46 through "the control, switch 49, conductor 82, coil of-relay-32, resistor 83, conductor'55, control switch '49 to the other secondary'terminalof the transformer 46., It will be observed'that under, normal conditions the .coil of the relay 32 is shunted by the'contacts 84' of the'control'relay 16 if the voltageof the' circuit 1 is above a predetermined value andby the contacts 85 of the control relay18'ifthe'voltage of the circuit 2 is above a predetermined value. Therefore, it is necessary for the voltages of both of these circuits to be below predetermined values in order for therelay. 32 to be energized. When the relay 32 is energized, it completes an energizing circuit for the control relay 33 from one secondary terminal of the transformer 46 through. the control switch 49, conductor 82, contacts 31 of relay 30,'conductor 87, coil ofirelay 33, conductor 88, contacts 89 of relay 32,'conductor 55, con-. trol switch 49 to the other secondary terminal of the. transformer 46. Relay 33 by closing its contacts'90 completes an energizing'circuit for the closing coil 34 of the switch 11 and'by closing its contacts 91 and '92, complete respectively energizing circuits for the controlrelays 2 2 and 24. The energizing circuit for the closing coil 34 of the switch 11 is from one secondary terminal of thetransformer 46 through control switch 49, conductor 82, contacts 90 of relay 33, conductor 93, closing coil 34 of switch 11, conductor 55, control switch 49' to the other secondary terminalof the transformer 46. The closing coil 34, when ;energized ,closes the switch 11 so that the auxiliary source 10 is connected to the connecting bus 7.

The energizing circuit for the control relay 22 v is from one secondary terminal of the transformer 46 through thecontrol switch 49, conductor 82, contacts 91 0f the relay 33, conductor 75, coil of relay22, conductor- 76, contacts 77 of lockout relay 40, conductor 55, control switch 49 to the other secondaryterminalof the transformer 46. Control relay 22 by closing it s contacts 7 8. completes an energizing circuit for the closing coil 23 of the switch 8 so that the circuit 1 is connected to the connecting bus 7. This energizing cir: cuit is from one secondary terminal, of the transformer 46 through the control switch 49, conductor 82, contacts 91 of relay33, conductor .75, contacts 78 of relay 22, conductor 54, contacts? 9 of relay 2 2, conductor 81', closing coil 23 of switch 8, con ductor 55, control switch 49 to the other secondary terminalof the transformer 46. p

The energizing circuit for the control relay 24 is from one secondary terminal of transformer 46 through control switch 49, conductor 82,contacts 92of relay 33, conductor 66, coil of relay 24, conductor 67, contacts 68 of lockout relay 42, conductor 55, control switch 49 to the other secondary terminal of the transformer 46. Relay 24, by closing its contacts69 and 70, completes an energizing circuit for the closing coil 25 of the switch 9 so that the circuit 2 is connected to the connecting bus 7. This energizing circuit isfrom one secondaryterminal of the transformer 46 through control switch 49, conductor 82, contacts 92 of relay 33, conductor '66, contacts 69 of relay 24, conductor62, contacts 0 of re lay 24, conductor-2'71, closingcoil 25 ofthe switch 9, conduc'tor 55, control switch 49 to the other secondary terminal of transformer 46. 7

Therefore, it will be observed that when the voltages of both of the circuits 1 and 2 arebelow predetermined values, the switches 8, 9 and 11 are closed to connect the auxiliary switch 10 to the circuits 1 and'2.

When the switch 11 closes its auxiliary conta'cts 98, it completes a circuit around the contacts 89 of relay 32 in the circuit of the control relay 33 so that the control relay 33 is not deenergized when the control relay 32 is deenergized in response to the energization of either the relay 16 or the relay 18 when the circuits 1 and 2 are reenergized. The switch 11 by opening its auxiliary contacts 53 and 61 prevents the control relays 17 and 19 from being energized in response to the energization of the circuits 1 and 2 whenthe switches 8 and 9 are closed.

If the fault on the circuit 1 has cleared prior to the closing of the switches 8 and 11, the switches 8, 9 and 11 remain closed and the auxiliary source 10 continues to supply cur rent toboth of the circuits 1 and 2. If, however, the fault is still connected to the circuit 1 when the switches 8 and 11 are closed the overcurrent through the switch 8 causes the lockout relay 40 to open its contacts 77 in the heretofore traced circuit of the closingcoil of t-herelay 22. The relay 22 by opening its contacts 78 and 79 opens the heretofore traced circuit for the closing coil 23 of the switch 8 to disconnect the faulty circuit 1 from the auxiliary source 10. Since the over-current which the auxiliary source 10 supplies to the fault circuit 1 does not flow through the primary winding of the transformer 43 the lockoutrelay 42 is not operated at this time to efiect the deenergization of the control relay 24 and the opening of theswitch 9 Therefore, the auxiliary source 10 continues to supply current to the normal circuit 2.

WVhen both of the circuitsl and 2 are independently energized and a fault occurs on the circuit 2 so that the source 5 is disconnected from the circuit 2 by the opening of the overload circuit breaker 6, the voltage relay 15 by closing its contacts 20 completes an" energizing circuit for the control relay 22. This energizing circuit is from one secondary terminal of the transformer through the control switch 47, contacts 51 of relay 16, conductor 52, auxiliary contacts 53 on switch 11, conductor 54, contacts 99 of relay 17, conductor 100, contacts 20 of relay 15, conductor 75, coil of relay 22, conductor 76, contacts 77 of lockout relay 40, conductor 55, control switch 47 to the other secondary terminal of the transformer 44. Control relay 22 by closing its contacts 79 completes an energizing circuit for the closing coil 23 of the switch 8 so that the circuit 1 is connected to the connecting bus 7. This energizing circuit for the closing coil 23 is from one secondary terminal of the transformer 44 through the control switch 47, contacts 51 of relay 16, conductor 52, auxiliary contacts 53 on switch 11, conductor 54, contacts 79 of relay 22, conductor 81, closing coil 23 of switch 8, conductor 55, control switch 47 to the other secondary terminal of the transformer 44.

' When the switch 8 closes, its auxiliary contacts 101 complete an energizing circuit for the control relay 24. This energizing circuit is from one secondary terminal of the transformer 44 through the control switch 47, contacts 51 of relay 16, conductor 52, auxiliary contacts 53 of switch 11, conductor 54, auxik iary contacts 101'on switch 8, conductor 102, contacts 103 of relay 33, conductor 66, coil of relay 24, conductor 67, contacts 68 of lockout relay 42, conductor 55, control switch 47 to the other secondary terminal of the transformer 44. Control relay 24 by closing its contacts 69 and 70 completes an energizing circuit for the closing'coil25 of the switch 9 so as to connect thecircuit 2 to the connecting bus 7. This energizing circuit for the closing coil 25 is from one secondary terminal of'the transformer 42 through the control switch 47, contacts 51 of relay 16, conductor 52, auxiliarycontacts 53 on switch 11, conductor 54, auxiliary contacts 101 on switch 8, conductor 102, contacts 103 ofrelay 33, conductor 66, contacts 69 of relay 24, conductor 62, contacts 70 of relay 24, conductor 71, closing coil 25 of the switch 9, conductor 55, control switch 47 to the other secondary terminal'of the transformer 44.

If the fault on the circuit 2 is cleared prior to the closing of the switches 8 and 9 these switchesre'main closed and the circuit 2 is supplied with current from the circuit 1. If, however, the fault is still connected across the circuit 2, the overload circuit breaker 4 is opened-as soon as the switches 8 and. 9 are closed so as to disconnect the source 3 from the circuit 1. Both of the circuits 1 and 2 are then deenergized and the auxiliary source 10 is connected to both of the sources in the manner above described. I If the fault is still connectedacross the circuit 2 when the switches 9 and 10 are closed, the lockout relay 42 operates to open its contacts 68 and effect the deenergization of the control relay 24 and the closing coil 25 of the switch 9 so that the circuit 2 is disconnected from the auxiliary source 10'.

While I have, in accordance with the patent statutes, shown and described my invention as applied to a particular system and as embodying various devices diagrammatically indicated, changes and modifications will be obvious to those skilled in the art and I, therefore, aim in the appended claims to' cover all such changes and modifications as fall within the true spirit i-and scope of my invention. r V V 7 What I claim as new and desire to secure by Letters Patent or" the United States, is;

v 1. In combination, two normally rdisconnected independently energized circuits, a source of current normally disconnected therefrom, and means responsive .to the voltages of said ,circuits for efiecting the eonnection of said circuits together when the voltage of one of said circuits decreases below a predetermined value while the voltage of the other circuit is above a predetermined value and for effecting the connection of both of said circuits to said source when the volt ages of both ofsaid circuits are simultaneously below predetermined values.

2. In combination, two normally'disconnected circuits, a connecting bus, a circuit breaker between said bus and'each circuit, means responsive to the voltages of said circuits for effecting the closing of said circuit breakers when the voltage of either of said circuits, decreases below a predetermined value while the voltage of the other circuit is above apredetermined value, a source of current, and means responsive to the voltages of said circuits for effecting the connection of said source to said bus and the closing of both of said circuit breakers when the voltages of both ofsaid circuits are simultaneouslybelow predetermined values. 1

In combination, two normally disconnected circuits, a connecting bus,a circuit breaker between said bus and each circuit,- means responsive to the voltages of said-cir cuits for efiecting the closing of each circuit breaker when the associated circuit voltage is above a predetermined value and the other circuit "voltage is below a predetermined value, means controlled by said circuit'breakers for effecting the closing of the other circuit breaker when one is closed, a source ofcurrent, a third circuit breaker for connecting. said source to said bus, means responsive to the voltages of-said circuits for effecting the closing of said thirdcircuit breaker when the voltages of both of said circuits are simultaneously below predetermined values, and means controlled by said third circuit breaker for closing both of said other circuit breakers when said third circuit breaker, is closed.

"-4. In combination, two normally disconnected circuits, aconnecting bus, a circuit breaker between said bus and each circuit, means responsive to the voltages of said circuits for effecting the closing of each circuit breaker when the associated circuit voltage is above apredetermined value and the vother circuit voltage has remained below a prede termined value for a predetermined time, a

source of current, a third circuit breaker for connecting said source to said bus, means responsive to the voltages of said c rcuits for effecting the closing of saidjthirdci'rcuit breaker when thevoltagesof both of said cir cuits remain below predetermined values for:

a predeterminedtime and meanscontrOlled by said third circuit breaker-for closing bothofsaid other circuitbreakers inresponse to the closing of said third circuit breaker and,

fecting the opening thereof in' response to I the current therethrough only when'saidcin cult breaker connects sa d source to sa d one of said circuits. v r

, 6.1n combination, two normally di'scon nected circuits, a sourc-eof current normally disc-onnectedfrom said circuits, an interconnecting bus, acircuit breaker between each circuit and said bus,;current responsive meansassociated with each circuit breaker. foreiiecting the opening thereoflmeans for connecting said source to said bus,aandl means for preventing each .overcurrent responsive m ansifroin efl'ectingtheopening ofits astedj circu t breaker in response to an overcurrent therethrough when said source is disconnected from said-bus.

,7. In combination, two normally discon; nected circuits, a source of current normally. disconnected from said circuits, an-interconnecting bus, a circuitbreakerbetween each circuit and said bus, overcurrent responsive means associated with each circuitbreaker for efiecting the opening thereof, acircuit breaker between said source and bus, and

means controlled, by said last mentioned'circuit breaker for short-circuiting, said over; current responsive means when said last mentioned circuit breaker is open, I 8.5111 combination, two normally discom nected circuits, a source of'current,- a plurality of switches controlled by thevoltages of said circuits for connecting 'sa id'circuits.

together whenthe voltage of one of said circuitsis below a predetermined value while the voltage of the other circuit is above a predetermined value and for connecting said source to both of said circuits when the voltages ofboth of said circuits are simultaneously below predetermined values, overcurrent responsive means associated with each of the switches which connects said cir cuits together for efiecting the opening thereof in response to the .current therethrough, and means for controlling the op eration of said ove-rcurrent responsive means so that they effect the opening of the associated switches only when said source is connected to one of said circuits.

9. In combination, two normally disconnected circuits, a connecting bus, a switch between each circuit and said bus, means responsive to the voltages of said circuits for effecting the closing of said switches when the voltage of one of said circuits is below a predetermined value while the voltage of the other circuit is above a predetermined value, a source of current, a circuit breaker for connecting said source to said bus, means responsive to the voltages of said circuits for effecting the closing of said circuit breaker and of said switches when the voltages of both of said circuits are simultaneously below predetermined values, means associated with each of said switches for efiecting the opening thereof in response to the current there through and for preventing the automatic reclosing thereof in response to the operation of said voltage responsive means, and means for controlling said opening means so that each effects the opening of its associated switch only when said source is supplying current to said bus.

10. In combination, two normally disconnected circuits, a connecting bus, a switch between each circuit and said bus, means responsive to the voltages of said circuits for effecting the closing of said switches when the voltage of one of said circuits is below a predetermined value while the voltage of the other circuit is above a predetermined value, a source of current, a circuit breaker for connecting said source to said bus, means responsive to the voltages of said circuits for effecting the closing of said circuit breaker and of said switches when the voltages of both of said circuits are simultaneously below predetermined values, means associated with each of said switches for efiecting the opening thereof in response to the current therethrough and for preventing the automatic reclosing thereof in response to the operation of said voltage responsive means, and means controlled by said circuit breaker for controlling said opening means so that each effects the opening of its associated switch only when said circuit breaker is closed.

In witness whereof, I have hereunto set my hand this 21st day of January, 1929.

ROBERT Y. MCCULLOUGH. 

